ISOPODS

Isopod

The most familiar isopod is the roly-poly bug you might see underneath an outdoor flowerpot. Sometimes called ‘potato bug’, ‘sow-bug’, or ‘pill-bug’, this terrestrial form is the exception. Most isopods are aquatic. These crustaceans are not actually insects. While insects have 3 pairs of legs the isopods have 6-7 pairs. Their segmented body is wide and flat with a series of plates running along the back. These small creatures are less than an inch long and many of them can be less than ¼ inch.

Fossil records of isopods go back to the Carboniferous period 300 million years ago. Today, thousands of terrestrial and aquatic species are found in all but the coldest parts of the world and in most habitats. In vernal pools, isopods can be omnivores, grazers and filter feeders inhabiting the leaf litter. They may eat algae and small organisms that cling to submerged rocks and logs. Tolerant of pollution and disturbance, they may be the only macroinvertebrates in contaminated pools.​Isopods are important scavengers in vernal pools decomposing and recycling detritus while helping to clean the water. They are an important food source for larger organisms including tadpoles and dragonfly larvae. You are not likely to notice them unless you explore the leaf litter at the bottom of the pool.

A great way to discover macro invertebrates of vernal pools, like the isopods, is to grab a handful of wet leaves and place them in a white tray, bucket or tub. Having enough water for them to swim around, slowly pick through the larger leaves and cast them aside. Soon, there will be few hiding places. In a healthy vernal pool, a wide variety of hidden wonders will be revealed. A magnifying glass, portable microscope or a camera with macro (close-up) lens can reveal even more. When done, submerge the container in the pool and let the contents gently wash away. Repeat as desired. A ‘D’ net or aquarium net can be used to sample, too. Have fun exploring your local vernal pools!